It is very common to store gasoline in underground storage tanks. Gasoline service stations, for example, typically, have several underground storage tanks, one for each grade of gasoline. Each of these underground tanks usually is located several feet beneath a concrete driveway or apron that surrounds one or more above-ground service islands that contain pedestal dispensing units for dispensing gasoline to automobiles and other vehicles. The pedestal dispensing units function to register the amount of gasoline dispensed and the cost of that dispensed gasoline. As is common, gasoline is dispensed from the pedestal dispensing units through hand-held dispensing nozzles that are inserted into vehicle gasoline tank fill pipes. The nozzles, each of which are connected to the pedestal units by a hose, include a hand-actuated valve for controlling the amount of gasoline dispensed. Each of the underground storage tanks is connected to one or more of the pedestal dispensing units that dispense the grade of gasoline stored in the tank by an underground fuel line. Pumps, located either in the storage tanks or in the pedestal units, pump gasoline through the underground fuel lines to the dispensing units.
Underground storage tanks of the type described typically are filled through an upwardly extending riser pipe that forms a portion of an inlet conduit for supplying gasoline to the tank. The riser pipe is in fluid communication with the interior of the tank and typically extends between the tank and a spill container that is located near the surface of the concrete apron. The spill container, which functions to protect the surrounding ground soil from spill contamination, extends to the surface of the concrete apron and is usually covered at the surface by a manhole cover. The upper portion of the riser pipe typically is threaded, and threadably receives an adapter for interconnecting the fill pipe to a hose from a tank truck. The adapter has a removable cap fitted thereon for sealing the inlet conduit when the storage tank is not being filled. The adapter and cap are contained within the spill container.
When filling an underground storage tank, the manhole cover is removed to gain access to the riser pipe adapter. After the seal cap is removed from the adapter, a hose from the tanker truck then is mechanically connected to the adapter, and gasoline is discharged through the hose to the inlet conduit and into the underground storage tank.
The lower portion of the adapter normally is sealingly engaged to the riser pipe, an extension of the riser pipe, or another inlet conduit component to prevent leakage of both gasoline flowing through the storage tank inlet conduit and gasoline vapor from the tank. However, prior art inlet conduit adapters have been plagued by the loss of that sealing relationship between the adapter and the inlet conduit. As a result of this sealing loss, gasoline and/or vapor leakage occurs at the adapter inlet conduit interface. Sealing loss between the adapter and inlet conduit is most commonly caused by relative rotation between those components. Unfortunately, rotational torque that tends to cause such relative rotation between the adapter and inlet conduit occurs very frequently in the process of filling an underground storage tank. For example, the rapid shutoff of an overfill valve in the storage tank will create line shock, and this line shock frequently tends to rotate the adapter relative to the inlet conduit. It also is common for truck drivers to move the distal end (the end proximate to the truck) of the tanker truck hose after it has been connected to the adapter, which movement applies a substantial torque on the adapter and tends to cause the adapter to rotate relative to the inlet conduit.
Various solutions to the problem of adapter/inlet conduit seal loss have been suggested. However, none of the previously attempted solutions have been completely successful. For example, it has been suggested that the adapter can be mechanically secured to either the riser pipe or spill container to prevent rotation of the adapter. However, since the seal of the adapter is tightened by rotating the adapter onto the riser pipe or other inlet conduit component, the exact angular position of the adapter in its fully tightened position is variable. Consequently, substantial complexity and expense is required to achieve the necessary adjustability for mechanically securing the adapter against rotational movement.